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It is probably most known for its kookaburra.
There are many, but the most famous being Detroit.
Automobiles.
Ontario, Canada, has more laws then any other city in the world making it the most governed city in the world.
It depends. You mean atmospheric, land or water pollutant? The most important would be carbon dioxide (CO2) from literally, millions of automobiles and industries.
Automobiles
it has to be California
Michigan
ford
As of 2013: Toyota
Both the city of Gary,Indiana and the city of Pittsburgh,PA
Bill Gates